May 9, 2011

Freshfield Glacier Retreat New Lake Forms

Posted by Mauri Pelto

The Freshfield Glacier in the Canadian Rockies retreat over the last five years has exposed a new glacier lake. . Today the glacier is 10.1 km long beginning at 3070 meters and ending at 1970 m near the shore of the less than 5 year old lake. This glacier during the Little Ice Age stretched 14.3 km, one of the longest in the entire range. By 1964 the glacier had retreated 1900 meters exposing Freshfield Lake. From 1964-1994 the glacier retreated up this lake basin losing another 1500 meters of length. A comparison of a 1964 photograph from Austin Post and as close to the same view as I could get in Google Earth illustrates the 45 years of retreat. The red line halfway up the lake is the 1964 terminus and the red line at the edge of the lake the terminus location in the topographic map. By the mid-1990’s the glacier no longer reached the shores of Freshfield Lake, as seen in the Canadian Topographic map, top image. In 2004 a satellite image (middle) indicates the glacier has retreated 400 meters from the lake but there is no sign of a second lake yet. In the current Google Earth Imagery a new lake has developed that is 370 meters across (bottom image), the new lake is marked N and Freshfield Lake (F). A 2012 Landsat image indicates that the glacier has retreated rapidly from the second lake, has continued and now terminates 1100 meters from the shore of Freshfield Lake. The glacier currently ends at 1970 m. Above the terminus there are two concentric depressions that typically indicate a depression beneath the glacier that would tend to at least seasonally fill with water. Such a depression cannot form except with a stagnating and rapidly retreating glacier tongue. This indicates that at least the next kilometer of the glacier will be lost quicly. In the terminus picture below the depressions are indicated by the letter B, and a nunatak poking out of the ice by the letter N. The map terminus is in red.. This glacier remains large and is not in danger of disappearing with present climate. Its behavior mirrors that of the Waputlik Icefield, but is less dramatic in terms of area loss than Warren Glacier or the disappearing Helm Glacier. Glaciers in Alberta as a whole are losing a much greater percentage of their area than Freshfield Glacier as reported by Bolch et al (2010)